Synthesis of the following classes of compounds was originally proposed: a) 2,4-Diamino-5-(1-adamantyl)-6-substituted pyrimidines; b) 2,4-Diaminio-5-substituted-6-methylpyrimidines with either (CHs)-Adamantyl or -CH2-NH-(CH2)2-Adamantyl at carbon 5; c) 2-4,Diamino-6-(or 7) substituted pteridines with either adamantyl or -CO-Adamantyl group at carbon 6 or 7, respectively; d) 2,4-Diamino- or 2-amino-4-hydroxylpteridines with -CH2NH-Adamantyl side chain at C-6; e) 5-Adamantyl-6-methylpyrimidines having an SH-group at C-2 and C-4 or Nh2-group at C-2 and SH-group at C4; f) 2,4-substituted purines having Adamantyl or -CH2-adamantyl group at N-9. Except for classes d, and e, some compounds of each class were synthesized. Compounds of group f were devoid of biological activity and thus this class was abandoned. Instead a new class of compounds, namely esters of 2,4-diaminopteorate is under development. Compounds most promising as potential antineoplastic agents appear to be: 2,4-diamino 5-adamantyl-6-methyl and 6-ethyl pyrimidines and 2,4-diamino-6-adamantylpteridine. The pharmacokinetics of these compounds will be investigated. Also, their uptake by the cells in vivo and their mode of action in rat tumors Walker Carcinoma 256 and Murphy-Sturm lymphosarcoma will be studied.